An image reading device for reading an image formed on an original document is mounted on a printer, a facsimile machine, or a multi function peripheral which has the functions of printing the image, to transmit the image via a line, and store the image in a memory.
The image reading device forms image data in the following steps: irradiating an original document with light; converting the reflected light intensity into voltage values using photoreceptors (line image sensors) arranged in lines; and then converting the voltage values into digital data.
The line image sensor is divided into a plurality of sections. The voltage values outputted from the sections are sequentially converted into digital data,
Japanese Unexamined Patent Application Publication No. 2001-136345 discloses an image reading device which sequentially reads signals from a plurality of sections of a line image sensor in synchronism with a given clock signal. In the image reading device, sections adjacent to each other in the length direction performs reading during a single reading period so as to partially overlap each other, thereby increasing its reading rate.